Fabrication technology and electrophysical properties of a composite memristor-diode crossbar used as a basis for hardware implementation of a biomorphic neuroprocessor

Abstract In order to build a biomorphic neuroprocessor hardware, a laboratory TiN/Ti0.93Al0.07Ox/p-Si/n-Si/W composite memristor-diode crossbar intended to serve as a basis for a memory matrix and a logic matrix, was manufactured. For this purpose, the materials and the fabrication nanotechnology for semiconductor layers of the Zener diode and a memristive layer, which ensured the required characteristics of the diode and of the memristors, were selected. It was demonstrated that the magnetron sputtering technology was unified both for the fabrication of the diodes and of the memristors. Therefore, all the layers in a composite memristor-diode crossbar, including conductive paths, can be fabricated in one technological cycle. Electrophysical properties of fabricated memristor-diode crossbar were investigated. Current-voltage curves of the memristor, of the diode and of the memristor-diode cell were measured. Signal processing was executed by the following procedures: output neuron pulses routing to other neurons' synapses; matrix-vector product, which is performed in the memory matrix while weighting and summing the signals; associative self-learning. It was the first time that the generation of a new association (new knowledge) in a fabricated memristor-diode crossbar of an artificial pulsed neural network was demonstrated, as opposed to associative self-learning in the existing hardware-based neural networks with synapses based on discrete memristors. The obtained experimental findings were compared with the SPICE simulation of the signal processing routines in a memristor-diode crossbar. The memristor parameter scatter at which the crossbar demonstrates stable operation was identified. The cells SPICE model was constructed from experimentally obtained i-v curve. The change in the output current of the cell, associated with the parasitic currents passing through the adjacent cells, was measured. It was demonstrated that the Zener diode parameters can reduce power consumption of the composite crossbar. The experimental findings highlighted that the composite memristor-diode crossbar intended to fabricate the memory and logic matrices of the neuroprocessor is essentially workable.